A confidence interval is a range of values used to estimate an unknown population parameter, such as a mean or proportion. It provides a way to express the uncertainty around a sample statistic. For example, if a survey finds that 60% of people prefer a certain product, a confidence interval might indicate that the true preference in the population is between 55% and 65%. The width of a confidence interval depends on the sample size and variability in the data. A larger sample size generally leads to a narrower interval, indicating more precise estimates. Researchers often use a confidence level, such as 95%, to signify how confident they are that the interval contains the true parameter.